Geschirrspueler mit sensoreinheit zur bestimmung einer drehbewegung eines sprueharms

ABSTRACT

The invention proposes a dishwasher comprising a working chamber ( 2 ), comprising at least one spray arm ( 5, 6 ) which is arranged in a rotatable manner in the working chamber ( 2 ), and comprising a metering apparatus ( 9 ) for supplying and metering a substance, such as detergent, rinse aid etc., into the working chamber ( 2 ), wherein the metering apparatus ( 2 ) is designed as an insert part ( 2 ) comprising a housing ( 20, 21 ) for insertion into a recess in an inner wall ( 7 ) of the working chamber ( 2 ), for example in the door ( 7 ) of the working chamber ( 2 ), and comprising a sensor unit ( 27, 28 ) for identifying a spray arm movement in the working chamber ( 2 ) of the dishwasher, which sensor unit is arranged at least partially in a housing ( 20, 21 ) of the metering apparatus ( 9 ), wherein the dishwasher has improved program control. According to the invention, this is achieved in that the sensor unit ( 27, 28 ) comprises at least one pressure sensor ( 27, 28 ) for detecting a water/liquid pressure.

The invention relates to a dishwasher comprising a working chamber and a sensor according to the preamble of Claim 1.

A dishwasher of this kind is described, for example, in DE 100 34 546 A1. In the case of this item according to the prior art, the interior of a dishwasher is monitored by means of one or more radar sensors using the Doppler effect. This sensor system is very complicated and accordingly costly. Furthermore, it has not been possible to realize technically problem-free functioning of a dishwasher of this kind to date.

The object of the invention is to propose a dishwasher having improved program control, proceeding from a dishwasher according to the preamble of Claim 1.

Proceeding from a dishwasher of the kind mentioned in the introductory part, this object is achieved by the features of Claim 1. Advantageous embodiments and developments of the invention are possible owing to the measures mentioned in the dependent claims.

Accordingly, a dishwasher according to the invention comprising a sensor unit for identifying a spray arm movement in the working chamber is distinguished in that the sensor unit comprises at least one pressure sensor for detecting a water/liquid pressure.

A sensor unit according to the invention can be used to check program sequences during operation. In particular, it is therefore possible to detect whether the spray arm and/or which spray arm is rotating properly or is malfunctioning.

Therefore, according to the invention, the pressure sensor can detect a change in pressure of a jet of water/liquid, that is to say a jet presses (more or less) on a pressure-sensitive sensor area of a sensor element of the sensor unit or there is no jet of water/liquid and therefore no pressure.

As an alternative to or in combination with this, according to the invention, the pressure sensor can detect a change in pressure of a volume of water/liquid, that is to say the variable volume or a different quantity/filling level of the water/liquid presses (more or less) on a pressure-sensitive sensor area of a sensor element of the sensor unit or there is no volume of water/liquid and therefore no pressure.

For example, at least a strain gauge, a piezosensor, a sensor which comprises a pressure-sensitive flexible diaphragm or the like can be used. Advantageous electronic signal processing or signal evaluation can be implemented in this way.

At least one inlet opening, through which a jet of water/liquid passes, of an interior of the housing and/or of the metering apparatus is preferably arranged at least partially in the jet of water/liquid from a spray nozzle of the spray arm during the rotation of the spray arm. Faults or incorrect measurements owing to water/liquid which does not arrive/originate directly from the rotating spray arm can be advantageously avoided/reduced in this way.

The arrangement according to the invention of the sensor unit and/or its sensitive sensor area/element “behind” the inlet opening of the interior of the housing and/or of the metering apparatus is achieved in that water/liquid/washing solution of the jet of water/liquid from the spray nozzle of the spray arm substantially or at least for the most part reaches the sensor unit and/or its sensitive sensor area/element. Owing to the arrangement according to the invention of the sensor unit and/or its sensitive sensor area/element in the/on the interior or its wall, water which drains off from the housing and/or from the metering apparatus and/or indirect water which splashes around or is deflected/reflected by washware does not reach the sensor unit and/or its sensitive sensor area/sensor element, or only a very small portion does so. A usable sensor signal can be generated in this way, which usable sensor signal advantageously exhibits a clear change with each rotation of the spray arm.

Therefore, for example in the case of the two-armed spray arms which are usually used in practice, rotate about a rotation axis and each have one or more spray nozzles, in particular arranged in the end section of the spray arm, a jet of water/liquid from the spray nozzle of the spray arm will enter the interior through the inventive inlet opening of the interior with each half-rotation according to the invention and reach/flow to the sensor unit and/or its sensitive sensor area/element and generate an advantageously evaluable sensor signal and, respectively, a significant/evaluable change in signal of the sensor unit and/or of its sensor element.

During normal or problem-free operation, a periodic signal or a periodic change in signal is present/can be detected according to the invention. In contrast, in the event of a problem, for example spray nozzle being blocked/damaged, rotation of the spray arm is adversely affected, in particular by improper positioning of washware in the region/path of the rotating spray arm etc., and the signal or the change in signal is not present or is only partially present and/or is non-periodic or exhibits (possibly additional) interference signals/changes in interference. This can be used, amongst other things, with the aid of an advantageous checking and/or evaluation unit for checking/controlling purposes and advantageously, for example, for optical and/or acoustic signaling or improved program control of the dishwasher. An operator can be prompted to examine the spray arm(s) for the proper state in this way.

In a particular variant of the invention, it is also possible, for example, for a (brief) increase in the pump pressure or the pressure of the jet of water/liquid from the spray arm to be provided for clearing the spray nozzle blockage or for “cleaning” the spray nozzle, so that (largely) automatic clearing of the detected/established fault/damage can be realized by the dishwasher according to the invention. Therefore, intervention by an operator may not be absolutely necessary. This increases the operational reliability of the dishwasher according to the invention and the convenience for the users/operators to a considerable extent.

The sensor unit is arranged at least partially on the outside and/or in the housing of the apparatus which is designed as an insert part and serves to supply and meter a working substance, such as a detergent, rinse aid etc. This means that, according to the invention, the pressure sensor can advantageously be arranged on the outside of the outer face/surface and/or on the inside in the interior of the metering apparatus or of the housing/insert part.

Within the meaning of the invention, an apparatus of this kind is called a metering apparatus. Furthermore, the terms “warewasher”, “dishwashing machine” and “dishwasher” are used synonymously in the present case, as are the terms “jet of water”, “jet of liquid” and “jet of washing solution”.

Within the meaning of the invention, the interior is designed substantially as a hollow space, channel, empty/air-filled chamber within the contour/circumferential surface of the housing and/or of the metering apparatus. Here, the advantageous inlet opening allows the jet of water/liquid to flow/enter the interior which is located/arranged within the contour of the housing and/or of the metering apparatus according to the invention. The interior advantageously forms a protective chamber or a chamber/region which is somewhat shielded and in which the sensor unit and/or its sensitive sensor area or the sensor element are/is at least partially protected/shielded, primarily against (indirect) splashing water or liquid not arriving/flying directly from the jet of water/liquid from the spray nozzle of the spray arm, that is to say liquid draining from a wall of the working chamber or liquid deflected by washware, etc.

A wall of the interior advantageously at least partially comprises the pressure sensor and/or a pressure-sensitive sensor area or diaphragm of the pressure sensor. A particularly low level of structural expenditure is possible in this way. Advantageous sealing off and/or welding/adhesive bonding or connection of the sensor area (which may possibly be produced from plastic) or diaphragm of the pressure sensor to the wall (which may possibly be produced from the same plastic) of the interior can also be implemented. This increases the operational reliability of the sensor unit and/or metering apparatus according to the invention.

In a preferred embodiment of the invention, the interior has at least one drain opening for draining/outflow of the water/liquid. The water/liquid entering the interior through the inflow opening according to the invention can advantageously flow out or be removed from the interior again by way of said drain opening. Therefore, water/liquid which has built up or the quantity of water/liquid present in the interior can be reduced or substantially cleared/removed in an emptying phase/period until water/liquid next flows in/enters (in an inflow/filling phase) from the (next) spray nozzle of the spray arm, that is to say usually after half a rotation of the spray nozzle of the second arm of the spray arm. This (clear/pronounced) change in the quantity/filling level of water/liquid in the interior according to the invention can advantageously be detected by sensor or by means of the sensor unit and/or its sensitive sensor area/element and used for advantageous program control.

In addition, the drain opening of the interior according to the invention advantageously reduces the structural and economic expenditure in comparison to active emptying, for example by means of pumping said water/liquid away using an electric pump, which is to be provided otherwise.

In general, the interior can be produced with an inflow opening and drain opening, for example by means of injection-molded plastic or the like, in an economically advantageous manner. For example, two or more wall parts of the interior may possibly be injection-molded and connected or welded to one another thermally or by means of adhesive. This allows the interior to be advantageously designed as a hollow chamber, channel, tube, funnel, collection pan or the like.

It is advantageous to set or to define the build up or the filling level/quantity of water/liquid in the interior and/or the duration/length of emptying or emptying phase. For example, it is possible to ensure or define that firstly enough water/liquid is built up or an advantageous filling level/quantity is (temporarily) stored in the interior, in particular by virtue of a relatively large or defined (clear) cross-sectional area of the inlet opening, and/or secondly the interior is as empty as possible or is largely empty until water/liquid next flows into/enters (in an inflow/filling phase). This improves the ability to detect an advantageous (periodic) sensor signal.

The drain opening advantageously has at least one restrictor apparatus for building up and/or restricting the water/liquid in the interior. The build up or residence time/temporary storage of the water or the liquid in the interior can advantageously be set/influenced by way of said restrictor apparatus. For example, an active restrictor element, such as a restrictor/blocking valve or the like, and/or a passive restrictor element, such as a narrow point or constriction/tapering of the (clear) cross section of the interior, can be provided according to the invention. The latter exhibits a particularly low level of structural and economic expenditure and advantageously forms the interior substantially as a funnel which drains automatically (with a delay).

The housing of the metering apparatus, which housing contains the sensor unit, is advantageously of water-tight design. In this case, accommodating the sensor unit in the housing of the metering apparatus which is present in any case makes it easier to arrange it in the interior of the working chamber of the warewasher. Firstly, it is not necessary to provide an additional opening in the inner wall or the door of the working chamber as a result of this since the metering apparatus is to be arranged in a recess in the inner wall of this kind in any case. Secondly, the housing is already of water- and washing solution-tight design in the case of the known metering apparatuses. All of the electrical control elements, even for the metering apparatus, which are located in the interior of the dishwashing machine door are already protected against the water or the dishwashing solution by the design of the housing according to the prior art.

Therefore, a sensor unit can advantageously be accommodated within a metering apparatus of this kind without relatively major sealing problems, wherein the inlet opening according to the invention is provided in the housing for example. An inlet opening of this kind in the housing or the interior according to the invention can be realized in a manner reliably sealed off from the (rest of the) housing wall of the metering apparatus simply by advantageous seals or else by integral forming/injection molding and/or fixed connection, for example by welding or adhesive bonding.

In an advantageous embodiment of the invention, the housing of the metering apparatus has guide elements in order to keep the interior and/or the sensor unit at least partially free of water running off from the housing, or furthermore the additional arrangement of guide elements is provided in order to keep water which is running off away from the inlet opening after passing through the spray arm. Water which is running down could cause a fault or disadvantageous inflow of water/liquid which does not arrive/originate directly from the spray arm, and this could generate undesired interference signals.

Owing to guide elements, for example in the form of a canopy above the inlet opening of the interior and/or above the pressure sensor and/or a pressure-sensitive sensor area of the pressure sensor, it is possible to ensure that water running down along the wall of the working chamber, such as along the door for example, is guided laterally around the inlet opening and/or around the interior and/or the pressure sensor or the pressure-sensitive sensor area of the pressure sensor. This increases the operational reliability of the dishwasher.

In an advantageous embodiment of the invention, guide elements of this kind are provided on the inner wall of the working chamber and/or on the door and/or substantially over the entire width of the housing or of the metering apparatus, as a result of which even the entire apparatus may possibly be protected against water which is running down and therefore the interior may possibly also be protected against undesired water or inflow.

The sensor unit is preferably arranged such that it is situated directly in a jet of water/liquid from a spray arm nozzle. Interference signals due to undesired accumulation of water/liquid are also reduced as a result.

A particularly high pressure on the sensor area and therefore a particularly strong/considerable or significant sensor signal can be generated the direct arrangement of the sensor unit or of the sensitive sensor area.

In a particular embodiment of the invention, the time sequence of the sensor signal is detected and an evaluation unit is provided in order to detect the periodicity or frequency of the sensor signal which is induced by the rotating spray arm.

Since the rotational movement of the spray arm is to be monitored according to the invention, it can be assumed that the signal is a periodic or frequency-dependent signal. Therefore, owing to the time detection of the sensor signals with subsequent evaluation in an electronic evaluation unit, the detected sensor signals can be selectively examined and/or evaluated for periodic signals or signal components (over a specific or prespecified time period). On account of this measure, virtually all non-periodically occurring interference signals can advantageously (already) be filtered or suppressed.

By virtue of determining the frequency, the rotation speed or speed of the spray arm can advantageously be determined. If necessary, checking/control/adjustment of the rotation speed or speed of the spray arm can be realized, for example by means of the pressure of the water/liquid acting on the spray arm/arms. If no periodic signal can be detected, this is a sign of a stationary spray arm, but at least of a non-freely rotating spray arm.

In the event of a malfunction of this kind of the spray arm, this can be, for example, displayed to an operator or else an intervention in the control of the program sequence can be made.

In a particular embodiment of the invention, an analog evaluation circuit is provided in order to detect the periodicity or frequency of the sensor signal which is induced by the rotating spray arm. A circuit of this kind can be realized, for example, using a so-called PPL (phase lock loop). Therefore, an oscillating input signal can be compared with the sensor signal in a comparator or differential amplifier and changes in the output voltage can be used to draw conclusions about proper rotation of a spray arm. Even if digital components are technically readily available for evaluating a sensor signal according to the invention, the use of an analog circuit may provide the technically more advantageous solution from cost points of view given appropriate numbers. The combination of an analog circuit with a digital evaluation arrangement, which intervenes only given a faulty output voltage of the analog circuit for example, would also be conceivable.

In the case of a digital evaluation unit, different algorithms can further be provided in order to analyze and to rule out disturbing influences. Instead of or in combination with the use of the periodicity as stated above, integration of the signal peaks, that is to say determining the area covered by the signal, for example, can also be used to identify and to rule out fault peaks. In this way, fault signals which do not follow the time sequence and the intensity of the signals generated by the spray arm or the jet of water or washing solution can be identified and ruled out. Threshold value analysis can also be used instead of or in addition to other fault identification methods.

An exemplary embodiment of the invention is illustrated in the drawing and will be explained in more detail below with reference to the figures.

Specifically:

FIG. 1 shows a schematic cross section through a warewasher comprising a spray arm,

FIG. 2 shows a schematic plan view of the inside of the door of a warewasher,

FIG. 3 is a schematic illustration of a metering apparatus in cross section together with a spray arm, and

FIG. 4 shows a schematic example of a sensor signal which can be generated by means of a pressure sensor.

FIG. 1 schematically illustrates a warewasher 1 comprising a dishwashing chamber 2 in section. Two dish racks 3, 4 are located in the dishwashing chamber 2, and a spray arm 5, 6 is arranged in a rotatable manner beneath each of said dish racks.

A warewasher door 7 is fitted to a front side of the dishwashing chamber 2 in a rotatable manner, as is indicated by a rotation axis 8. A metering apparatus 9 for adding dishwashing agent is located in the warewasher door 7.

A sump container 11 is located in the base 10 of the warewasher 1, said sump container containing, for example, the customary filters and a water outlet 12.

FIG. 2 shows the arrangement of the metering apparatus 9 in a plan view of the door 7. The metering apparatus 9 is inserted into the warewasher door 7, as already described with reference to FIG. 1. The metering apparatus 9 comprises a housing upper part 20 of a housing 21 and, on its top side in a customary manner, a flap 14 or cover 14 for closing a dishwashing agent chamber and a flap 13 for closing a rinse aid chamber.

An evaluation and control unit 18 or an operator control unit 18 for the user/operator can also be arranged in the interior of the warewasher door 7, as indicated in FIG. 1. In the location of the evaluation and control unit 18 indicated in FIG. 1, said evaluation and control unit can be connected directly to the displays, buttons and other operator control elements required to operate the machine.

FIGS. 2 and 3 additionally illustrate the arrangement of an inlet opening 17 and a drain opening 15 of an interior 22 according to the invention of the metering apparatus 9. In FIG. 2, a canopy 16 or a drip tray 16 is arranged separately above the inlet opening 17. In FIG. 3, the canopy 16 or the drip tray 16 is integrated/integrally formed virtually in the form of a “nose” or drain protection means directly in/with a housing upper part 20 of the housing 21 or is designed as an upper edge of the inlet opening 17 of the interior 22 according to the invention of the metering apparatus 9. The canopy 16 serves as a guide element in order to divert water or washing solution which is running down.

As is clear primarily in FIG. 3, a jet 23 of water or liquid from a spray nozzle 24 which is arranged on the end of the rotating spray arm 5, 6 passes directly through the inlet opening 17 into the interior 22 of the apparatus 9. Other jets 29 of water or liquid from spray nozzles 30 which are arranged more centrally on the rotating spray arm 5, 6 do not pass through the inlet opening 17 into the interior 22 of the apparatus 9.

The water/liquid/washing solution which has entered the interior 22 collects in a build-up region 25 which has a restrictor point 26 or narrow point 26 on its lower section, so that the water/liquid collects/builds up in the interior 22 (in a defined manner) as schematically depicted. A drain 27 comprising the drain opening 15 of the interior 22 is provided “behind” or “beneath” the narrow point 26 in the direction of flow.

The narrow point 26 has a prespecified clear/free cross section, so that, by virtue of the spray arm 5, 6 which rotates past, enough water/liquid collects/builds up above the narrow point 26 in order to detect the presence of the jet 23 of water or liquid or the presence of the built-up water/liquid in the build-up region 25 using a first pressure sensor 27 or alternatively a second sensor 28.

The pressure sensor 28 is preferably used in the impingement region of the jet 23 of water or liquid from the spray nozzle 24 which is arranged at the end of the rotating spray arm 5, 6. The water/liquid flows away automatically through the drain or the outflow opening 15, so that the build-up region 25 is emptied again or the filling level of the built-up water/liquid drops again and therefore the build-up pressure is reduced or completely relieved. This build up and outflow takes place periodically in the case of a properly rotating spray arm 5, 6.

The sensor 27 can, for example the pressure which is proportional to the filling level or to the level of the built-up volume or water/liquid, likewise be designed as a pressure sensor 27 according to the invention. That is to say that, in particular, the different level of the build-up region 25 enables advantageous pressure measurement by means of the sensor 27.

In principle, a pressure sensor 27 and primarily a pressure sensor 28 which is arranged directly on the impingement region of the jet 23 can be used to detect and evaluate both a rotation of the rotary arm 5, 6 and advantageously a pump pressure or water/liquid pressure. Therefore, a pump pressure or pressure of the jet 23 is substantially proportional to the sensor signal P (cf. FIG. 4). A conclusion about or monitoring of the pump or its function, in particular problem-free operation, can advantageously be generated as a result.

FIG. 4 illustrates, by way of example, a time sequence of a pressure sensor signal of the pressure sensor 28. The horizontal axis of the graph shows the time t, while the vertical axis illustrates the intensity I. The sensor signal exhibits different peaks P1 to P5 which are arranged periodically as a function of time t. The respective time points t1 to t5 are correspondingly marked.

The graph according to FIG. 4 shows, by way of example, two further peaks S1, S2 and S3 which constitute interference signals which can be caused, for example, by undesired impingement of jets of water/liquid which are deflected at the washware, or the like.

These interference peaks S1, S2 and S3 can be identified and eliminated by suitable evaluation by means of the evaluation unit 18. This evaluation can be configured, for example, in such a way that only periodically recurring signals P1 to P5 are perceived as real sensor signals, non-periodic signals however being perceived as interference signals. Another way of identifying the interference signals involves, for example, integrating the corresponding signal peaks with respect to time, as a result of which the area which is covered by the peaks is mathematically determined. Since an integral value is to be expected within a specific interval given regular sensor signals, other signals, such as the linear interference signals S1 and S2 for example, can be identified and ruled out in this way.

These exemplary methods or else further methods for identifying interference signals, for example by means of threshold values in respect of the intensity or the like, can be used on their own or else in combination with one another. FIG. 4 illustrates, by way of example, a threshold value L which is used for separating off or filtering interference signals and the desired signals.

If a malfunction, for example a stationary spray arm or a spray arm which is rotating too slowly, is identified on the basis of the sensor signal, this can be displayed to the operator in a display or by the operator control unit 18.

The warewasher according to the invention can also be controlled depending on the sensor signal. For example, the quantity of water and/or the pump pressure can be varied. Nozzles which are controllable in respect of the orientation of the jet and/or shape of the jet are also optionally conceivable.

LIST OF REFERENCE SYMBOLS

-   -   1 Warewasher     -   2 Dishwashing chamber     -   3 Dish rack     -   4 Dish rack     -   5 Spray arm     -   6 Spray arm     -   7 Warewasher door     -   8 Rotation axis     -   9 Metering apparatus     -   10 Base     -   11 Sump container     -   12 Outflow     -   13 Flap     -   14 Flap     -   15 Outflow opening     -   16 Canopy     -   17 Inlet opening     -   18 Evaluation and control unit     -   20 Housing upper part     -   21 Housing     -   22 Interior     -   23 Jet of water     -   24 Nozzle     -   25 Build-up region     -   26 Narrow point     -   27 Sensor     -   28 Sensor     -   29 Jet of water     -   30 Nozzle     -   t Time     -   I Intensity     -   L Threshold value     -   P1 Peak     -   P2 Peak     -   P3 Peak     -   P4 Peak     -   P5 Peak     -   t1 Time point     -   t2 Time point     -   t3 Time point     -   t4 Time point     -   t5 Time point     -   S1 Interference peak     -   S2 Interference peak     -   S3 Interference peak 

1. A dishwasher comprising a working chamber (2), comprising at least one spray arm (5, 6) which is arranged in a rotatable manner in the working chamber (2), and comprising a metering apparatus (9) for supplying and metering a substance, such as detergent, rinse aid etc., into the working chamber (2), wherein the metering apparatus (2) is designed as an insert part (2) comprising a housing (20, 21) for insertion into a recess in an inner wall (7) of the working chamber (2), for example in the door (7) of the working chamber (2), and comprising a sensor unit (27, 28) for identifying a spray arm movement in the working chamber (2) of the dishwasher, which sensor unit is arranged at least partially in a housing (20, 21) of the metering apparatus (9), characterized in that the sensor unit (27, 28) comprises at least one pressure sensor (27, 28) for detecting a water/liquid pressure.
 2. The dishwasher according to claim 1, characterized in that at least one inlet opening (17), through which a jet (23, 29) of water/liquid passes, of an interior (22) of the metering apparatus (9) is arranged at least partially in the jet (23, 29) of water/liquid from a spray nozzle (24, 30) of the spray arm (5, 6) during the rotation of the spray arm (5, 6).
 3. The dishwasher according to claim 2 wherein a wall of the interior (22) at least partially comprises the pressure sensor (27, 28) and/or a pressure-sensitive sensor area of the pressure sensor (27, 28).
 4. The dishwasher according to claim 3 wherein the interior (22) has at least one drain opening (15) for draining/outflow of the water/liquid.
 5. The dishwasher according to claim 1 wherein the housing (20, 21) of the metering apparatus (9) has guide elements (16) in order to keep the pressure-sensitive sensor area and/or the pressure sensor (27, 28) and/or the interior (22) at least partially free of water running off from the housing (20, 21).
 6. The dishwasher according to claim 5 wherein at least one outer wall of the metering apparatus (9) and/or of the housing (20, 21) at least partially comprises the pressure sensor (27, 28) and/or a pressure-sensitive sensor area of the pressure sensor (27, 28).
 7. The dishwasher according to claim 5 wherein the guide elements (16) are designed as a roof (16) over the inlet opening (17) through which the jet (23, 29) of water/liquid passes and/or over the interior (22).
 8. The dishwasher according to claim 1 wherein the sensor unit (27, 28) is arranged such that it is not situated directly in a jet (23, 29) of water/liquid from a spray arm nozzle (24, 30).
 9. The dishwasher according to claim 1 wherein a time sequence of the sensor signal is detected and an evaluation unit is provided in order to detect the periodicity and/or frequency of the sensor signal which is induced by the rotating spray arm (5, 6).
 10. The dishwasher according to claim 1 further comprising an analog evaluation circuit.
 11. A metering apparatus (9) for supplying and metering a substance, such as detergent, rinse aid etc., into a working chamber (2) of a dishwasher according to one of the preceding claims, which metering apparatus is designed as an insert part (9) comprising a housing (20, 21) for insertion into a recess in an inner wall (7) of the working chamber (2), for example in the door (7) of the working chamber (2), and comprises a sensor unit (27, 28) for identifying a spray arm movement in the working chamber (2) of the dishwasher, which sensor unit is arranged at least partially in the housing (20, 21), characterized in that the sensor unit (27, 28) comprises at least one pressure sensor (27, 28) for detecting a water/liquid pressure. 